The overall goal of this proposal is to evaluate the ability of therapeutic vaccinations to help control HIV/AIDS in the more than 40,000,000 people who are already infected. Our hypothesis is that a vaccine can elicit cell-mediated immunity capable of providing better viral control than the functionally limited T cells characteristic of chronic SIV infections. Our approach will be to (i) treat SIV239 infected rhesus macaques with anti-retroviral therapy to reduce viral loads and allow at least partial CD4 T cell recovery, (ii) vaccinate animals while they are on anti-retroviral therapy to elicit high quality CD4 and CD8 T cells, and (iii) interrupt therapy to assess efficacy as measured by set point levels for re-emergent virus. A SIV239 DNA/MVA vaccine will be evaluated for therapeutic potential. The prototype for this vaccine elicits high frequencies of CD8 and CD4 T cells in uninfected macaques. Preliminary studies indicate that the DNA/MVA vaccine in combination with drug therapy can elicit robust CD4 and CD8 T cells in infected macaques and improve viral control following treatment interruption. In this project, we seek funds to extend these studies to a larger cohort of macaques and for longer periods of study. The best success in therapeutic vaccination regimens has been with autologous in vitro-cultured dendritic cells (DC). We hypothesize that immunogens and adjuvants that enhance DC function in vivo can elicit therapeutic responses. Specifically, we propose to test the ability of CD40 ligand and the toll- like receptor 7 agonist imiquimod to serve as adjuvants for the DNA/MVA vaccine in a therapeutic setting. This choice of adjuvants focuses on remediation of known CD40/CD40L deficits in SIV infection. In specific aim 1 we evaluate the therapeutic potential of the non-adjuvanted and adjuvanted DNA/MVA vaccine in combination with anti-retroviral therapy (ART) in SIV239 infected macaques and test the hypothesis that the frequencies of polyfunctional CD4 and CD8 T cells determine viral control. In specific aim 2 we characterize DC following SIV infection, drug therapy and vaccination to better understand the relationship between DC, cellular immunity and viral control, and test the hypothesis that failure of DC function contributes to impaired T cell function and that restored DC function supports the elicitation of polyfunctional T cells. In specific aim 3 we evaluate mucosal sites for temporal viral loads and SIV-specific immunity to understand how therapeutic vaccines affect the balance of virus and immune responses in the major mucosal reservoirs for infection.